1. Field of the Invention
The present invention relates to a time information obtaining apparatus receiving a standard time radio wave to obtain the time information thereof, and further relates to a radio wave timepiece mounted with the time information obtaining apparatus.
2. Related Art
Now, long wave standard time radio waves are transmitted from transmitting stations in each of Japan, Germany, the United Kingdom, Switzerland, and the like. For example, in Japan, standard time radio waves of 40 kHz and 60 kHz subjected to amplitude modulations are transmitted from transmitting stations in Fukushima Prefecture and Saga Prefecture, respectively. Each of the standard time radio waves includes a row of codes constituting a time code indicating a year, a month, a day, a time, and a minute, and is adapted to be transmitted in the period of 60 seconds. That is, the period of the time code is 60 seconds.
Timepieces (radio wave timepieces) capable of receiving a standard time radio wave including such a time code, of extracting the time code from the received standard time radio wave, and of correcting the displayed time thereof have been put to practical use. A receiving circuit of a radio wave timepiece includes a band-pass filter (BPF) for accepting a standard time radio wave received with an antenna to extract only a standard time radio wave signal, a demodulator circuit demodulating the standard time radio wave signal subjected to an amplitude modulation by envelope detection or the like, and a processing circuit reading the time code included in the signal demodulated by the demodulator circuit.
A conventional processing circuit performs in order a process of second synchronization processing, minute synchronization processing, code capturing, and consistency judgment after the detection of a standard time radio wave. If any pieces of the processing have not be appropriately ended, then the processing circuit has to recommence the process from the beginning. Consequently, the processing circuit may have to recommence the process many times owing to the influences by the noise included in a signal, and then a period of time until the time information can be obtained may become remarkably long.